The present invention refers to a method of and apparatus for rehabilitating a track bed. In particular, the present invention refers to an improved method of stabilizing the subgrade of a track, including a continuous removal of ballast from underneath the track to expose the subgrade while simultaneously blending additives to the exposed subgrade underneath the track for formation of a new protective layer through subsequent leveling and consolidation, with removed and possibly cleaned ballast being subsequently laid over the protective layer. This invention also related to an improved arrangement for carrying out this method.
Austrian Pat. No. 294,898 discloses an arrangement for simultaneous cleaning ballast of track beds and stabilizing the subgrade. The arrangement includes an elongated machine frame which is supported by bogies on its ends. Approximately in the center of the machine frame is a track lifting device which is preceded in operating direction by two like excavating chains mounted to the machine frame and guided for placement underneath the track. Ballast is picked up by the leading one of the excavating chains for transport of ballast to a screening unit for removal of fouling material while the cleaned ballast is returned to the track by a conveyer and laid via a spreader over the track bed. The trailing second excavating chain cuts and receives subgrade of a certain layer thickness. Excavated soil is elevated and unloaded on a conveyer belt by which ballast residues received from the screen are transported at the same time. Subsequently, this material is discharged either outside the track or deposited on a conveyer which is additionally supplied with additives and cement from a container. The resulting mixture of soil, ballast residues, additives and cement is laid over the track bed via a flexible boom in operating direction before the discharge area of the cleaned ballast and blended by a motor-driven rotating member. Subsequently, the mixture is compacted and stabilized by a vibrating plate compactor. This method is relative cumbersome and the arrangement is of complicated structure so as to be highly susceptible to failures and prone to malfunction.
European Patent specification EP 0135478A1 discloses a method for stabilizing soft soils for improving its support capability. After removing the layers covering the subgrade, the underlying ground is mixed on site with cement and lime as well as with water and other substances to reinforce and promote stability.
Swiss Pat. No. 595,512 discloses a method of and apparatus for stabilization of the surface area of a subgrade by disposing an unfoamed diffusable high resistance foam over the subgrade and expanding the foam to form a load-carrying band without any gaps.